The second heart sound in patients with tetralogy of Fallot
may be single and loud, and a harsh systolic ejection murmur
will be present, emanating from the obstructed subpulmonary
outflow tract. Flow across the interventricular
communication in tetralogy of Fallot is usually not turbulent,
and therefore not audible. Patients with severe
obstruction, and very little antegrade flow across the subpulmonary
outflow tract, will be more significantly cyanotic
and have a less prominent murmur.